Tuesday, April 27, 2010
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1. Moisture conservation & retention
So, that leads to your next question – what really happens if I have too much mulch?
1. Enough mulch = water retention; too much mulch = soggy soil & wet bark. Research has shown that azalea, rhododendron, and yews suffer most from extended periods of continuously wet soils. Also, if mulch is piled up against the stem of these plants, it will lead to constantly wet bark and the potential for disease development.
2. Wet soil = hungry roots. The ground accumulates layers of decomposing mulch that become wet and virtually seal the soil surface. Roots under a sealed surface layer become starved for the oxygen necessary for growth and development. A weakened root system can lead to poor foliage, late or sporadic flowering, weak stems and smaller leaves on new growth.
On the topic of too much mulch, let's discuss tree volcanoes. I’m sure you’ve seen trees in your neighbor’s yards with so much mulch piled around the base that it looks like a volcano? This should be fixed as soon as possible. The tree bark will decompose under the layer of mulch and may result in an open wound (canker) in the bark that doesn't heal. This breaks the essential connection between the food producing foliage and the nutrient absorbing root system. Research has shown that flowering cherry, dogwood and ash trees seem to be most susceptible to this type of bark injury.
When thinking about buying mulch, we warn you to be aware of the bright orange mulch that appeared on the market a couple years ago. You may not realize it, but it isn’t real bark mulch; just ground up wooden pallets spray-painted to look like mulch. Recycled wood products are no substitute for bark mulch; the two are distinctively different. Remember what we said earlier about bark mulch retaining moisture? Well, recycled wood products don’t.
For the overall health of your shrubs, be aware of your mulch depth. If the mulch beds tend to be over 3 inches deep, remove the excess mulch and reapply no more than 1.5 inches. A one-time removal procedure can be a labor-intensive job, so the best way to prevent this from happening in the future is to ensure that mulch removal is included in your spring clean-up each year.